下列四种合同中，属于单务合同的是（ ）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='26220' and id < 2196127 and id<>'2196127' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='26220' and id > 2196127 and id<>'2196127' order by id asc limit 5